Download Nervous and Endocrine Systems

Nervous System
Nervous System
 Responds to stimuli to maintain
homeostasis.
 Stimulus (Stimuli) = a signal to which an
organism reacts
 Response = some action or movement
of an organism brought on by a stimulus
Nerve cells
 The cells of the nervous system are
called neurons.
 Neurons carry messages called
impulses
 Nerves = send messages to the spinal
cord, muscles, and glands for response
The Neuron
Cell body (cyton):
contains nucleus, cell organelles; site
of metabolic activities
Nucleus :
contains the genetic material
Dendrite:
receives impulses from other neurons
and carries them toward the cell body
The Neuron
Axon:
carries impulses away from the cell
body
Schwann cell nucleus
Schwann cell:
surrounds the axon; produces the
myelin sheath
The Neuron
node of Ranvier:
gap between neighboring
Schwann cells
Myelin sheath:
insulation that increases
the speed at which the
impulse can travel
The Neuron
Terminal branches
the axon terminates (ends)
with the terminal branches
Synaptic knobs:
release neurotransmitters
into the synapse
The Neuron
 Synapse: small gap between two
successive neurons
***Neurotransmitters are chemicals
used to transmit an impulse from the
axon of one neuron to the dendrites of
the next neuron
Types of Neurons
 Sensory Neurons: transmit impulses
from sensory organs (receptors) to the
spinal cord and brain
Sensory organs: eyes, ears, nose,
mouth, skin
Types of Neurons
 Motor Neurons: transmit impulses from
the spinal cord and brain to muscles
and glands (effectors)
Types of Neurons
 Interneurons: connect sensory and
motor neurons
 Found ONLY in the Central Nervous
System (brain and spinal cord)
Reflex Arc
 Receptorsensory neuroninterneuronmotor
neuroneffector
Reflexes
 Automatic responses to stimuli
 We do not have to think about the response
 They are inborn
 All connections have been formed by the time
we are born
 They are fast
 They take the shortest path
 The speed of the response is protective
reflex arc animation
Central Nervous System
 Part of the nervous system that contains
the brain and spinal cord.
The Brain
 Coordinates all of your body activities
 The brain is made of 100 billion neurons
 Interprets stimuli, sends impulses to the
body
Cerebrum
 Largest part of the brain
 Thinking takes place here
 Controls:
 Memory
 Movement
 Thinking
Cerebellum
 Coordinates voluntary
muscle movement
 Maintains muscle tone
 Maintains balance
 Receives stimuli from
eyes, ears, muscles, and
tendons.
Brain Stem
 Located at the base of the brain
 Connects the brain to the spinal cord
 Contains:
 Midbrain and Pons = pathways connecting
various parts of the brain with each other
 Medulla = controls involuntary actions
Spinal Cord
 Extension of the brain stem
 Made of bundles of neurons that carries
impulses to all parts of the body
The peripheral nervous system (PNS)
 All the nerves that
extend out of the
brain an spinal cord
 Most of the PNS is
under your direct
control
THE PNS
 Autonomic Nervous System: controls
body activities that are involuntary
 Contractions
of heart muscle
 Movement of smooth muscles
Disorders of the Nervous System
 Alzheimer's Diseases
 A progressive disease that destroys
memory and other important mental
functions
 Brain cell connections and the cells
themselves degenerate and die
 There is no cure
Disorders of the Nervous System
 Amyotrophic Lateral Sclerosis (ALS)
 Weakens muscles and impacts physical
function
 Nerve cells break down, which reduces the
function of muscles.
 There is no cure for ALS
Disorders of the Nervous System
 Epilepsy
 A disorder in which nerve cell activity in the
brain is disturbed, causing seizures
 Can be caused by genetics or a brain
injury
 Treated by medications, surgery, devices,
or dietary changes
Disorders of the Nervous System
 Meningitis
 Infection and inflammation of the
membranes surrounding the brain or spinal
cord
 Vaccines can prevent some forms of
meningitis
 Depending on the cause, it may get better
on its own, or it can be life-threatening
Disorders of the Nervous System
 Multiple Sclerosis
 Our WBCs attack and destroy Schwann
cells
 This slows down the impulses from
neurons